Recent comments in /f/askscience

IsraelinSF t1_j1vgo9c wrote

Reply to comment by BarberOk271 in AskScience AMA Series: I'm Here to Talk About Roots and Shoots: How Plants Prosper in the Desert and What it Means for Agriculture and Biodiversity, AMA! by AskScienceModerator

Plants in the desert are similar to others. There is a large variety in the desert, all different in their mechanisms. Many desert plants are C4 and CAM plants. CAM is an acronym for crassulaceae acid metabolism. C4 and CAM plants are considered to be more tolerant to arid conditions such as drought, salinity, and high temperatures. Cacti are just one group of CAM plants. Plants in general when they open their stomata to absorb CO2 they lose water. CAM plants open their stomata at night, thereby minimising water loss. In C4 plants the enzyme that first takes in CO2 from the atmosphere is more efficient and therefore the time that the stomata opens can be shortened. . An example of C4 plants in maize, or corn. There are also many C3 plants that have specific adaptations, from being an annual that only grows for a short time when there is rain, to being very tolerant to salinity, nutrition deprivation, high light, and many other such adaptations.

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IsraelinSF t1_j1vgfmz wrote

Reply to comment by darthvirgin in AskScience AMA Series: I'm Here to Talk About Roots and Shoots: How Plants Prosper in the Desert and What it Means for Agriculture and Biodiversity, AMA! by AskScienceModerator

Here is an example from one of our previous responses: One annual plant in the Negev, called Salsola Inermis, was the first plant I studied as a researcher in the Negev. The uniqueness of this plant is that it is a summer annual desert plant, meaning it grows in summer months when there is no rain at all. It germinates at the end of March when there is minimal rain then grows to maturity in the summer, in an area that is very deprived of nitrogen. Two main factors for the plants in the desert is lack of water and nitrogen, making this plant special. With UC Berkeley we managed to find for the first time that this species uses water from dew. They distinguish dew from other water through the different chemical characteristics of hydrogen and oxygen in water. In addition, we found a unique three-way symbiosis between Salsola Inermis, weevils, and nitrogen fixing bacteria that live in the guts of the weevil. We showed that the weevils contribute nitrogen to the Salsola Inermis which they get from the bacteria, and the Salsola Inermis contributes sugars to the weevils in addition to water from the dew. All three organisms benefit.

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IsraelinSF t1_j1vg5mt wrote

Reply to comment by RavenousOwlhead in AskScience AMA Series: I'm Here to Talk About Roots and Shoots: How Plants Prosper in the Desert and What it Means for Agriculture and Biodiversity, AMA! by AskScienceModerator

In the desert you will find a large variety of plants from annuals to perennials to flowers and many others - cacti are just one example. In deserts in Israel, cacti are a minority. Plants can be divided into three categories. The most common are C3 plants, which make up 85% of species and biomass. The rest of the species can be categorised into two groups: C4 plants and CAM plants. C3 plants get their name because the carbon product produced is a three carbon product. Similarly, C4 are called that because they produce a four carbon product. CAM is an acronym for crassulaceae acid metabolism. C4 and CAM plants are considered to be more tolerant to arid conditions such as drought, salinity, and high temperatures. Cacti are just one group of CAM plants. Plants in general when they open their stomata to absorb CO2 they lose water. CAM plants open their stomata at night, thereby minimising water loss. In C4 plants the enzyme that first takes in CO2 from the atmosphere is more efficient and therefore the time that the stomata opens can be shortened. . An example of C4 plants in maize, or corn. There are also many C3 plants that have specific adaptations, from being an annual that only grows for a short time when there is rain, to being very tolerant to salinity, nutrition deprivation, high light, and many other such adaptations. Other adaptations include unique symbiosis with the rhizosphere and other organisms. One annual plant in the Negev, called Salsola Inermis, was the first plant I studied as a researcher in the Negev. The uniqueness of this plant is that it is a summer annual desert plant, meaning it grows in summer months when there is no rain at all. It germinates at the end of March when there is minimal rain then grows to maturity in the summer, in an area that is very deprived of nitrogen. Two main factors for the plants in the desert is lack of water and nitrogen, making this plant special. With UC Berkeley we managed to find for the first time that this species uses water from dew. They distinguish dew from other water through the different chemical characteristics of hydrogen and oxygen in water. In addition, we found a unique three-way symbiosis between Salsola Inermis, weevils, and nitrogen fixing bacteria that live in the guts of the weevil. We showed that the weevils contribute nitrogen to the Salsola Inermis which they get from the bacteria, and the Salsola Inermis contributes sugars to the weevils in addition to water from the dew. All three organisms benefit.

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lookmeat t1_j1vds4s wrote

Reply to What is the ‘widest’ ancestral generation? by vesuvisian

In theory it's around the area that the generation side spreads to larger than the population, in practice this won't matter much since the size of disconnected populations that su but reach a branch is tiny compared to the greater world, unless you happen to be a member of that specific branch. The other factor is that incest probably covers a good chunk of that tree, which child reduce how quickly your tree widens (that is there could be multiple people in your tree that only have two grandparents) so technically our generation exponentiation is not 2, but some slightly smaller number (the average). It probably is very close to 2 though, so it should be a good enough estimate. Another factor that we're not considering is that not everyone reproduced, and that we really want the population that reproduced, but that's hard to measure and the number is probably pretty close to the total population.

So you find the average gap between generations, lets say 17 years (consider that for the greatest amount of time people got married at 13 and it was common to have had most of your children before 20). So it's mapping the population in year *x* vs *((YOB-x)/17)^2* where *YOB* is the year you where born. The x` is almost certainly with an error of 10 years, though it could easily be a century before you even hit the millennia. I am sure you won't go to BCE, and I'd be surprised if the year was any time before 500CE.

A more interesting question is: assuming modern family conventions, and generally full population mix, how long would it take until someone is probably a descendants of everyone that reproduced?

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IsraelinSF t1_j1vdko6 wrote

Reply to comment by Wrong_Swordfish in AskScience AMA Series: I'm Here to Talk About Roots and Shoots: How Plants Prosper in the Desert and What it Means for Agriculture and Biodiversity, AMA! by AskScienceModerator

Humans and plants have a mutual effect on each other. Just walking in the desert could have direct effects such as changes in soil structure and germination, as well as indirect effects in the rhizosphere. Anything from walking to building to the use of cars can have these effects.

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IsraelinSF t1_j1vd7a4 wrote

Reply to comment by Randombleizinthewild in AskScience AMA Series: I'm Here to Talk About Roots and Shoots: How Plants Prosper in the Desert and What it Means for Agriculture and Biodiversity, AMA! by AskScienceModerator

Plants can be used to prevent desertification. The Great Green Wall in the Sahara is an example, which was an initiative by the UN and the UNCCD (UN Convention for Combatting Desertification). Plants stabilise the soil, fertilise the soil, and can allow for other plants to grow by changing the climate and soil conditions, including the chemical and physical structure of the soil. Using native plants is optimal when possible. The climate can change with trees, which will cool the area - In a model if you remove trees you decrease precipitation and increase temperatures. Trees affect the climate in many aspects, through immediate cooling effects as well as long term CO2 sequestration, which reduces CO2 in the atmosphere.

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